The present invention relates to a particulate product form such as a granule comprising a high concentration of a colorant pigment system or a combination of an inorganic material, such as calcium carbonate, and a colorant pigment system, which may be organic or inorganic, or a mixture of both, and which granule may be blended with a thermoplastic polymer, such as polyolefin to produce a final thermoplastic end product. The blend produced will result in a homogenous composite after being processed using conventional methods such as blow molding, injection molding, and extrusion to produce a final thermoplastic end product. The invention allows both an inorganic filler material and a colorant pigment system to be internally formed into a granule which is used directly in thermoplastics without the need for a separate mixing process. The invention provides a means of achieving high concentrations of inorganic filler material and at the same time add a colorant pigment system to the thermoplastics thereby reducing the number of additives which are generally added separately to the thermoplastic feed for the thermoplastic process.
The thermoplastic processing industry has used inorganic filler materials and optionally a particulate colorant system as additives for thermoplastic resins. Generally these filler materials and colorant pigment system are added separately to the thermoplastic feed. Introduction of the inorganic materials into the polymer has traditionally been achieved using a number of techniques, including those described below.
a) The polymer, inorganic filler material and other additives may be subjected to intensive mixing using mechanical systems designed to disperse the inorganic filler material and additives in the polymer at a temperature above the melting point of the polymer. The proportion of inorganic filler material and additives in the mixture of polymer, inorganic filler material and additives is the same as that required in the final product. Suitable mixing equipment includes internal mixers of the Banbury type, twin or single screw extruders and continuous or batch compounders. Once the inorganic filler material has been dispersed, the melted mixture must be converted into a particulate product form such as granules which will facilitate subsequent processing, e.g. injection molding or extrusion. PA0 b) The polymer, inorganic filler material and other additives are mixed in a similar way to that described above, except that the inorganic filler material is first surface treated with a hydrophobic material to render it compatible with organic polymers. Examples of such hydrophobic materials include carboxylic acids of moderate to high molecular weight such as butyric, lauric, oleic and stearic acid, organosilane coupling agents, organotitanates and zircoaluminates. The proportion of inorganic filler material and other additives in the mixture of polymer, inorganic filler material and additives is much higher than is required in the final product. Inorganic filler material concentrations in the order of 75 to 80 weight percent may be produced using this technique. Mixtures with inorganic filler material contents above this level become both difficult to produce and difficult to redisperse in subsequent processing steps. The final particulate product (e.g. granules) is blended with unfilled thermoplastic polymer immediately prior to entering the final processing operation in such a ratio as to produce a mixture with a lower inorganic filler material which is uniformly distributed and dispersed throughout the system. PA0 c) Highly concentrated, redispersible inorganic filler material compositions are described in U.S. Pat. No. 4,803,231 which have inorganic filler material contents in excess of the 75 to 80% by weight achievable using conventional methods. This patent describes a composition which contains three components: (1) a polyolefin polymer or blend of polymers between 19.99 and 4.05 percent of the composition; (2) 80 to 95 percent inorganic material; and (3) an agent which renders the mixture fluid (a fluidifacient) included at 0.01 to 0.95 percent. This fluidifacient is described as an orthophosphoric acid ester with the general formula: ##STR1## Where A represents ethylene oxide, B represents propylene oxide, 0&lt;(m+n)&lt;24, R represents an alkyl group (which may be linear or nonlinear, and may be saturated or unsaturated), an aryl group, or a heterocycle (which may be saturated or unsaturated), wherewith said alkyl, aryl or heterocycle group has 5-28 C atoms, preferably 8-24 C atoms, or R is a steroid group; wherewith further the group R may be branched or unbranched and/or may have one or more functional groups, for example, Halogen, --OH, --COOH, --COOR, --NO.sub.2, --NH.sub.2, --CONH.sub.2, --CN or OPO.sub.3 H.sub.2, AND R' may be hydrogen, a carbon chain having 1-4 C atoms, or a group R as defined supra. Thus it is possible that the group R' is identical to the group R. PA0 d) European Patent Application No. 0355808 describes the use of a mixture of a fatty acid salt in combination with a fatty acid amide in the ratios between 10:90 and 90:10 as a coating for calcium carbonate to reduce the surface tension of the inorganic material surface. This coating was also evaluated as a replacement for the orthophosphate ester described in U.S. Pat. No. 4,803,231 (described above) with a view to producing a redispersible composite.
This composition may be blended with unfilled polymer prior to entering the final processing operation in such a ratio as to produce a mixture with a lower inorganic filler material content which is uniformly distributed and dispersed throughout the system. The resultant mixture contains a reduced level of the polyolefin polymer used for preparation of the concentrate as a result of the increased concentration of inorganic filler material. In discussing this invention in the common assignee's Canadian Patent Application No. 2016447 (the discussion is of equivalent patent EP 0 203 017) it is observed that although a theoretical level of filler of up to 95 percent is disclosed, a practical limit is only 88% by weight of calcium carbonate. In addition, the use of relatively toxic phosphate esters limits the applicability of this system to non-food contact systems.
The aforementioned Canadian Patent Application No. 2016447 describes a process used to produce a redispersible composite which uses a volatile solvent to prepare the product. This solvent and moisture are eliminated, leaving an inorganic material containing a hydrophobic coating in a hydrophobic binding agent. The composition of this product after elimination of solvent and dispersing agent is claimed to be 92.1-96.1% inorganic material, 0.1-3.0% of a hydrophobic surface coating agent and 3.8-4.9% of a hydrophobic binder system. This product may be added directly to thermoplastic systems in such proportion as is required by the final formulation. The reduced binder content allows addition to flame retardant polymer systems without adversely influencing flame retardancy. The volatilization step used in this process tends to introduce undesirable complexity and costs.
The fillers which may be mineral are added to the host thermoplastic during thermoplastic processing systems such as injection, blow molding, or extrusion. Optimum levels of the fillers range from 10 to 25 weight percent based on the weight of the host thermoplastic, dependent on application, i.e. the final form of the final thermoplastic end product.
The above prior art relates to the use of high binder contents which is introduced into the final polymer composition; or to the use of dispersion or fluidifacient additives or agents which allow a highly concentrated inorganic filler material composite to be produced which will redisperse with ease in thermoplastic polymers. If a colorant pigment system is desired in the final polymer composition, then generally, it is added as a separate additive to the polymer composition.